The present invention relates to a capacitor and more particularly, to a through-type capacitor for use in electrical and electronic equipment.
Following the recent tendency to miniaturization of circuit construction for various electrical and electronic equipment and devices, capacitors of compact size, especially through-type capacitors, have been widely employed in various fields of electrical and electronic industries.
Referring to FIG. 1, there is shown the construction of a known through-type capacitor, which generally comprises an annular metallic housing H having an upper opening Ho1 and a lower opening Ho2 with a smaller diameter than Ho1; a capacitor element EC including a disc D of ceramic dielectric material which has a central bore Do; a ring-shaped electrode e1 provided around the central bore Do at the upper surface of the disc D; another ring-shaped electrode e2 provided on the lower surface of the disc D adjacent to the peripheral edge thereof and which is accommodated in the opening Ho1 of the housing H; and a central rod-shaped conductor member A inserted into the central bore Do of the disc D, in which position it is secured. The central conductor member A is electrically and mechanically connected, at its collar portion Ac, to the electrode e1 by soldering or the like as at e1s, while the bottom Ha of the housing H between the openings Ho1 and Ho2 is also electrically and mechanically connected to the electrode e2 by soldering or the like as at e2s. The housing H is filled with resin material r, which serves both as electrical insulation and as outer cladding.
The conventional through-type capacitor as described in the foregoing, although extremely simple in its structure, has various disadvantages.
(i) When the through-type capacitor is to be attached, for example, to an electronic equipment chassis (not shown), the solder e2s connecting the metallic housing H and the electrode e2 tends to melt due to the heat of the soldering iron or other instrument used which can cause shortcircuiting between the central conductor member A and the metallic housing H.
(ii) To extend the working frequency of the above kind of through-type capacitor to the GHz range, it is necessary to reduce the thickness of the ceramic dielectric disc D to the order of 200.mu.. When the capacitor element Ec is so thin, it may in some cases crack when the lower end portion of the central conductor member A is bent toward the left or right for connection to a circuit (not shown).
(iii) The work of filling the metallic housing H with resin r especially through the lower opening Ho2, is very difficult due to the small diameter of the opening Ho2, etc., and hardening of the resin tends to be insufficient in some cases, resulting in reduction of withstand voltage or poor insulation, unless resin material r is inserted at least three times. Moreover, when resin material r is inserted via both the upper and lower openings Ho1 and Ho2, the resin material inserted through one hole must be sufficiently dried before resin can be inserted through the other, and thus, extra working hours are required, with consequent increase of the manufacturing cost.